How to detect sulfuric acid dew point corrosion in refining equipment
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Considering the background of sulfuric acid dew point corrosion in refining equipment mentioned earlier, detection can be carried out using the following methods: Online acid dew point monitoring – By utilizing conventional conductive acid dew point meters, the sampling probe is inserted to a depth of 1/3 of the flue length; the temperature of the probe is controlled by adjusting the cooling airflow. When the electrode current stabilizes within the range of 40–60 μA, the corresponding temperature is recorded as the real-time acid dew point. Parameters such as oxygen content and humidity can also be monitored simultaneously, making this method suitable for use in explosion-proof environments such as heating furnaces and waste heat boilers in refineries. Offline sampling and laboratory analysis involve taking samples of the deposits in the corroded areas; by determining the proportion of sulfur in these deposits as well as their layered structure (loose grayish-black outer layer and dense whiteish-luminous inner layer), and combining this with metallographic analysis, it is possible to determine whether it constitutes typical sulfuric acid dew point corrosion, thereby aiding in identifying the root cause of the failure. Routine equipment inspection and troubleshooting rely on the regular monitoring of VOC concentrations in refineries; portable detectors are used to detect organic compounds that leak out due to corrosion in the equipment, thereby identifying hidden corrosion points and allowing for the early detection of potential issues. Linkage verification of process parameters: By utilizing operational data such as the heating furnace’s thermal efficiency and flue gas temperature, and by comparing the measured acid dew point with theoretically calculated values (such as the Muller-Totman formula), it is determined whether the current operating conditions fall within a range where dew point corrosion is likely to occur.
The poster’s sharing is very practical; in particular, the specific operating parameters for conductive acid dew point meters (probe insertion depth, current stability range) are explained clearly, which is of great value as a reference for actual field operations. I would like to add two points of experience: the position of the sampling probe is crucial; in addition to depth, care must be taken to avoid areas with stagnant smoke or vortex zones, otherwise the measured dew point temperature may be too low. It is recommended to select several more measurement points in the straight sections of the flue and where the airflow is stable for comparison. When taking samples offline, be careful of corrosion products: the sediment may contain concentrated sulfuric acid or sulfurous acid; it is essential to wear acid-resistant gloves and goggles when sampling. The sample should be analyzed as soon as possible after being sealed, to prevent further corrosion or changes in its composition. Additionally, in high-temperature flue gas environments, it is advisable to use stainless steel 316L or higher-grade Hastelloy for the probe material; otherwise, the probe itself is prone to corrosion, which affects its lifespan. The above are merely personal experiences; for specific operating conditions, it is recommended to refer to the equipment manual or consult a professional instrument manufacturer.